1. Field of the Invention
The present invention relates to a method of recording, as an image file, a subject image shot with a digital camera, a method for playback display of the recorded image file by uploading it to a personal computer (PC) or the like, and a system and apparatuses for implementing the methods.
2. Description of the Related Art
Image data shot with a digital camera are typically converted into JPEG format and recorded on a recording medium or the like in an image file format. The DCF standard specifies rules for ensuring image file compatibility among digital cameras of different manufacturers and the EXIF standard specifies rules for recording shooting-related information, such as the shutter speed or shooting date and time data, while ensuring information compatibility. Therefore, data interchangeability is ensured by these standards even if photos are taken with a digital camera of any manufacturer, facilitating user convenience. When image data shot with a digital camera are stored in a storage device in a personal computer (PC) or the like, a folder is generally created on the PC and the image data are copied to the created folder to store and record them as image files. In this recording method, however, since the date and time of creation of the recorded image data is set as the date and time at which the image data were stored and recorded on the PC from the digital camera, the date and time of shooting with the digital camera cannot be known from the recorded image files, making it difficult to manage the image files in order of shooting date and time.
In order to enable sorting of image data in order of shooting date and time, for example, Japanese Patent Application Laid-Open No. 2000-322300 describes that upon reading and recording image data stored in a digital-still camera, the time stamp of a file to be recorded is changed to shooting date and time data on the camera. This publication also describes that the file name and the folder name can also be set as the date and time of creation of the image data, i.e., as the shooting date and time on the camera. During shooting with a digital camera, shot images are recorded as image files on a recording medium loaded or built in the digital camera. At this time, in order to ensure the compatibility of image files, a recording format and the like are typically prescribed pursuant to each of the above-mentioned standards. The shooting date and time is recorded in each image file together with its file name so that upon playback display of the image, the shooting date and time is also displayable on a screen. There have been needs to display the shooting date and time together with the image since long ago, and even many of film cameras have a function for optically recording the shooting date and time on a film upon exposure so that the user can figure out the shooting date and time on its print.
In the meantime, many people go abroad nowadays on business or for pleasure, and when going abroad where there is a difference in time, some confusion exists about shooting date and time, causing a problem. For example, assuming that a user departed from Japan at 18:30 on January 15 and arrived in San Francisco after eight hours of flying, the arrival time in San Francisco is 2:30 on January 16 in Japan Standard Time. However, since there is a time difference of 17 hours between Japan and San Francisco (i.e., in San Francisco, it is 17 hours later than in Japan), the local time in San Francisco is 9:30 on January 15. It means that the local arrival time is earlier than the departure time from Japan on the same day. In generally, since travelers adjust their schedule to the local time, they usually set their watches or the like to the local time upon or immediately before the arrival at the local place.
As for a digital camera carried abroad with a user on his-or her trip, if the clock time set in a clock function built in the camera to decide on the shooting time to be recorded in each image file is not changed at all, the time for each shot image is all recorded in Japan Standard Time, and displayed in Japan Standard Time upon image playback. Therefore, for example, the time displayed on an image shot in the daytime at a local sightseeing place could be a midnight time due to a time difference from Japan. In such a case, it cannot be denied that there is a sense of discomfort between the time displayed together with the image and the image content. At the local place, since the user has set his or her watch to the local time to adjust his or her schedule to the local time, it is desirable that the time displayed together with the playback image should be represented in the local time. In order to avoid causing this sense of discomfort, the clock time set by the clock function built in the digital camera has only to be changed to the local time. However, in the above example, the departure time from Japan is 18:30 on January 15, while the local arrival time is 9:30 on the same day. In this case, for example, an image shot at the time of departure from Japan is dated January 15, 18:30. Suppose here that the user adjusted the time clock of the digital camera to the local time on an airplane during eight hours of flying, and took a picture with the digital camera when the airplane landed at the airport in San Francisco. In this case, the image shot upon arrival is dated January 15, 9:30. Since the shooting time of the image shot upon arrival is inconsistent in terms of the order of shooting, the order of shooting time of the recorded image does not match with the order of actual shooting date and time, thus causing confusion.
After taking a large number of pictures abroad and going back to Japan, if the user uploads the images to a personal computer or the like for playback display, the order of shooting will become inconsistent with the order of shooting time as mentioned above, ending in undesirable results. If the user took pictures with a single digital camera, the image data representing those pictures can be played back in order of image file name to display the images in order of shooting. However, if the user took pictures with plural digital cameras, e.g., two digital cameras, the images cannot be displayed in order of actual shooting even if they are played back in order of image file name. This point will be described in detail below. Here, it is assumed that two digital cameras made by manufacturer A are used to take pictures.
The details of a file name deciding method vary from manufacturer to manufacture. For example, a digital camera of manufacturer A assigns file names starting from DSCP0001, incrementing the number part by one from the second file name, like DSCP0002, DSCP0003 . . . . Similarly, a digital camera of manufacturer B assigns file names starting from KIMG0001, incrementing the number part by one like KIMG0002, KIMG0003 . . . . Further, a digital camera of manufacturer C assigns file names starting from G1125001, which is followed by G1125002 . . . in a like manner, except that the first four digits “1125” represent the shooting date. In this case, date information is acquired at the time of shooting from clock means built in the digital camera, and the file name is decided based on the date information. The last three digits represent a number part independent of the date, starting from “001” and followed by “002”, “003” . . . . For example, suppose that the first and second frames are shot on November 25 and the third frame is shot on November 26. In this case, respective file names are G1125001, G1125002, and G1126003.
Japanese Patent Application Laid-Open No. 10-177646 discloses a technique teaching that basic information for creating a file name is not reset so that serial numbers (numbers in consecutive order) are assigned across different recording media even if a recording medium is replaced with another as long as shooting is continued with the same digital camera. This function is a very commonly employed technique, and it is assumed here that the two digital cameras of manufacturer A used in the following example have this function so that consecutive file numbers will be assigned.
For example, suppose that the user went abroad with two digital cameras of manufacturer A and took pictures using the two digital cameras in combination. Suppose also that the file names of image files shot with one digital camera are DSCP0114 to DSCP0120 and the file names of image files shot with the other digital camera are DSCP0001 to DSCP0009. Suppose further that, after the total of 16 pieces of image data are uploaded to a PC and stored in a single folder for collective management, the image data are playback displayed in order of file name. Since the order of playback display of the image files is determined according to the alphabetical order and numeric order of the characters forming a character string of each file name, DSCP0001 is first displayed, followed by DSCP0002, DSCP0003, . . . , DSCP0009, then DSCP0009 is followed by DSCP0114, DSCP0115, DSCP0116 . . . , and DSCP0120 comes last. In this case, the order of image display will be inconsistent with the order of actual shooting unless after pictures corresponding to DSCP0001 to DSCP0009 are taken with and recorded on the first camera, the user changes the camera to the second camera to take pictures corresponding to DSCP0114 to DSCP0120. Further, even if the image files are sorted in order of shooting time prior to playback display, the order of shooting time is inconsistent with the order of actual shooting because of the time difference as mentioned above. Therefore, the sorted order does not match with the order of actual shooting. The fact is that it is impossible for the conventional technique to perform playback display of the image files in order of actual shooting after all.